With Leonard Nimoy’s passing, the original Spock will not grace the screen again. I want to take this moment to explain what he has meant to me as a scientist.

Nimoy was much older than I, but Spock and I are contemporaries. I was born in 1967, while the original Star Trek ran for three seasons, 1966-1968. Then it was canceled, and only became seriously popular in reruns, in the 1970s. I first saw it at the age of about seven or eight. It was on every evening at that time, as I recall. I watched it most nights, becoming obsessed.

Spock was my favorite character from the beginning. I dressed as him for Halloween when I was nine. My mom got me the ears, and the insignia patch, which she sewed onto a blue long-sleeved jersey like Spock’s, and I think I had a phaser and tricorder. This was, without question, the high point of my Halloween costume career.

What was it about Spock that was so appealing? It was not nearly as crude as the trademark dialogue about “logic”.

Yes, Spock was an outsider, not in on the jokes of the popular, fun crew members, many of which were at his expense. And yet he managed to stay cool, earn everyone’s respect, and fit in in his own way, and with that he warmed the hearts of nerds watching everywhere. And yes, the plots in which his strongest emotions showed – where he let on how much he cared about Kirk, especially – said something genuine about the fundamental importance of friendship and love, corny as some of those moments were.

But to me, most of all, he was important as a scientist character in the popular culture, and as such he was a complex and true role model.

Spock’s brilliance was not mechanical; it was not just technique. He was creative, bold. His genius lay in generating the ideas as much as in using logic to follow them to their conclusions or test them against evidence. “Speculate, Mr. Spock,” was a request Kirk made in more than a couple of episodes. Spock complied not as an officer obeying a command, but as someone being freed, given license. Spock was calm in the exercise of his powers of deduction and calculation – as when drawing Kirk’s gentle amusement with his excessively precise estimates of probabilities – but his eyes lit up and his voice became electric when new understanding struck, causing him to utter his expression of scientific passion: “Fascinating”.

Spock was ethical. In “Devil in the Dark”, he and Kirk are charged with exterminating a creature that tunnels through rock and has been killing human workers under the surface of a mining colony. As he and Kirk are trying to figure out how to kill the creature, Spock realizes that it may be the last of its species, and thus that to kill it would be “a crime against science”. Later, Spock uses the Vulcan mind meld – a capability, exercised in a few episodes, that demonstrated as literally as possible that he did not just live in his own head – to determine that the creature has been acting in self-defense; the miners had been destroying its eggs.

Though Spock sometimes did seem clueless about social cues and insensitive to the emotions of others, he had moments of profound empathy, even without using the mind meld. The episode “Amok Time”, in which Spock goes into heat and has to go back to Vulcan for a mating ritual, has a subplot about Nurse Chapel’s feelings for him. (I know, the original Star Trek was not great in the roles for women department.) Spock is holed up in his quarters, his hormones driving him nuts, and Miss Chapel tries to bring him his favorite homemade Vulcan soup. He angrily rejects her advance, throwing the full soup bowl out of his door and against the corridor wall.

Later, she comes into his quarters again while he is sleeping. She tries to touch him, can’t bring herself to do it, and turns to leave, tear-eyed. He wakes, and in a moment of clarity he says, looking her right in the eyes: “Miss Chapel. I had the most startling dream. You were trying to tell me something, but I couldn’t hear you.” They have an exchange in which he tries to let her down easy (he is bound by law and genetic urge to the bride on Vulcan towards whom the Enterprise is aimed at high warp), expressing tenderness through his calm rationality. He ends by asking that she make him the soup after all. He understands that to make it for him is what she needs, and he cares, even though he’s not into her. Her face, turned away from him but showing joy to the camera as she leaves, shows that he has asked in just the right way.

Finally, of course, Spock was not just a supporting character. He saved the day in many episodes, through both bravery and science. He made us young science geeks think that we could be heroes even if we lacked Kirk’s suave charisma, and he did it without being a dysfunctional or arrogant jerk like Sherlock Holmes, House, or many of the other scientist types on TV.

Perhaps what was most compelling about Star Trek, and what seems so romantic now, was that Spock was in the position to be a hero in the first place. He had the clout on the Enterprise that he needed to hold Kirk and the others to his high standards of intellectual honesty and ethical behavior. More than the scientist as technical problem solver, Spock was the scientist trying to use reason in order to figure out how to live by principles, collectively as well as individually, and succeeding at it.

As scientists, we want what we do to matter. In the 21^st century, we face science denial on climate, vaccines, and evolution, and a broad anti-intellectualism and lack of respect for reason, in Congress and in a significant portion of the culture at large. The societal rationality that Spock embodied, much more than the transporters or warp drives, seems the most utopian thing about the 23^rd century portrayed in Star Trek.